IBI Bill

This will be the first year we are responsible for paying this and I can't work out when it is due or quite how to set about getting it. When we bought the house last year, we got a copy of last year's payment dated Nov 2014. Other things I have read online suggest it is billed June to August of each year and I can be fined 20% if I don't pay it by the due date, does this sound right?? Can anyone shed any more light? We are under the Ajuntament of Llucmajor. Thanks!